This application requests funds for the purchase of a phosphorimager for UCLA. This instrument is designed to replace conventional X-ray film-based autoradiography for imaging, analyzing and quantitating beta-radiation. The source of radiation is placed in contact with an imaging screen to form a latent image on the screen. The imaging screen is "developed" after an appropriate exposure time by a laser scanner which "releases" the image in the form of photons. Information from the photon detector is stored digitally where it is ready for quantitative analysis or display. The advantages of the phosphorimager over traditional methods are several: 1) increased sensitivity by a factor of 10-200 over traditional methods, 2) a linear response range for data collection that is greater than that for X-ray film by a factor of 10-3 - 10-4, and 3) data storing and processing capabilities that make it possible to objectively quantify signals over the dynamic range of the instrument from a single exposure. These features make previously impractical experiments "doable", they allow the experimenter to extract quantitative information from the stored data and they make it possible to normalize and compare multiple samples. The research descriptions of the major users (Courey - PI - Transcriptional Control of Pattern Formation in the Drosophila Embryo, Berk - Regulation of Transcription by Adenovirus, Clarke - Control of Eukaryotic Membrane Function by Methylation, Gober - Generation of Asymmetry During Caulobacter Development, Gralla - Mechanism of Transcriptional Initiation, Gunsalus - Regulation of Cellular Respiratory Functions, Johnson - Mechanism of site-specific DNA recombination and growth phase regulation by Fis, Merchant - Metalloprotein Biosynthesis in Chlamydomonas, Miller - Invasion of epithelial cells by Yersinia and Salmonella, Morrison - Regulation of Antibody Biosynthesis and Function, Sigman -Chemical Nucleases as Probes of Nucleic Acid Structure-Function Relationships, Simons - Translational Control and RNA Structure, Tobin - Phytochrome Regulation of Specific Gene Expression, Valentine -Functional Studies of Cytosolic Anti-Oxidant Proteins, Weiss - Metabolic Organization in Neurospora) justify the use of the instrument to enhance their research capabilities on each of their NIH-funded research projects. A plan for makihg the instrument available to the large community of researchers in the biomedical sciences at UCLA is in place and resources for its long-term operation and maintenance are guaranteed. The technology is well-developed and has been employed in basic biomedical research for many years. The users include a large group of active investigators, all of whom are engaged in research on health-related, NIH-funded projects representing studies on fundamental aspects of biochemistry, molecular, cell and developmental biology. By enhancing the effectiveness of the research efforts on these individual projects, this application benefits and su orts health-related research.